Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/12/20
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
552 PM MDT Fri Sep 11 2020
.AVIATION...
00Z TAF CYCLE
VFR conditions are expected for the next 24 hours. High altitude
smoke will continue to cross the southern half of the forecast area.
Winds should be less gusty on Saturday than they were today.
44
&&
.PREV DISCUSSION...254 PM MDT Fri Sep 11 2020...
.SYNOPSIS...
Temperatures will continue to trend warmer into the weekend. Upper
level smoke will drift into the Land of Enchantment from the west,
remaining mostly aloft. Dry and clear conditions will prevail next
week. The exception will be some spotty showers and thunderstorms
across the southwest and south central mountains each day through
Tuesday. Temperatures will continue to trend up through the end of
the week, as upper level high pressure elongates in the Desert
Southwest.
&&
.DISCUSSION...
SHORT TERM...(TONIGHT THROUGH SATURDAY)...
Deep layer, dry westerly flow over NM has mixed to the surface with
lcl breezes at several locales, especially eastern NM. Temps have
trended much warmer today with only a few thin cirrus and some cu
near the high terrain. A thick veil of upper level smoke has shifted
into the southern half of NM from massive wildfires burning over CA.
The 12Z-18Z HRRR smoke guidance shows this smoke remaining aloft,
however high level smoke will make for brownish skies with haze
increasing over the region. Flow aloft will veer west to northwest
Saturday as a strong upper level ridge slides east from the Great
Basin. This will force most of the smoke into southern NM Saturday.
Temps will trend warmer again Saturday but still remain 5 to 10F
below normal. A weak northeast wind shift will slide into eastern NM
as surface high pressure builds down the Front Range. No impacts to
sensible weather are expected with the boundary other than a few
more afternoon cu.
LONG TERM...(SUNDAY THROUGH FRIDAY)...
High pressure in the Great Basin meanders east on Sunday, as energy
from the base of longwave trough across the Great Plains breaks off
to form a low over northern NM. This setup will create a Rex block,
which will allow dry air to prevail over the majority of the CWA,
while modest moisture near the low increases precip potential. While
the return flow remains meager, daily showers and thunderstorms are
possible each afternoon through Tuesday across the southwest and
south central mts. By midweek, the upper high will push east,
overtaking the low, and becoming the dominant feature through the
rest of the week. Temperatures will trend up, as dry and clear
conditions prevail into the weekend.
Guyer/12
&&
.FIRE WEATHER...
Dry westerly flow over NM has trended temps warmer with lower RH and
local breezy winds today. Thick smoke aloft from CA will stream over
NM thru Saturday before shifting southward Sunday. A weak upper
level wave will develop over the region this weekend and drift
southwest thru next week. There is little moisture to work with so
mostly afternoon clouds are expected near the mountains and perhaps
an isolated shower each day. Light winds and weaker m
Guyer
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service La Crosse WI
1030 PM CDT Fri Sep 11 2020
.SHORT TERM...(This evening through Saturday)
Issued at 210 PM CDT Fri Sep 11 2020
Main forecast focus is on the rain/storms into Saturday.
Water vapor imagery as of early afternoon shows a deep closed upper
low across the central high plains with a plume of moisture
advecting north ahead of the trough into the Upper MS Valley.
Isentropic ascent/moisture transport will ramp up through the late
afternoon and evening with showers becoming more widespread and
spreading north and east through late day as a weak embedded
shortwave trough lifts across the area. Precipitable water values
will increase to around 1.75 inches this evening with a deep warm
cloud layer. A limiting factor for heavy rainfall amounts will be
the weak instability, with MUCAPE of only a few hundred J/kg. As a
result, expect mainly periods of showers tonight with embedded
storms. Rain amounts of generally 1/2 to an 1.5 inches are expected
from northeast IA through central WI , with isolated amounts of 2+
inches possible mainly over northeast IA and far southwest WI, and
lower amounts farther west across parts of southeast MN. Do not
anticipate much of a flash flood threat, but some rises on rivers
and streams are possible. Temps overnight tonight should remain
fairly steady with persistent warm advection.
Precip will diminish Saturday morning as the slug of isentropic
ascent/moisture transport pushes off to the east. A few additional
showers through the afternoon are possible as the upper low
approaches. Highs on Saturday are expected to be in the 60s for much
of the area.
.LONG TERM...(Saturday night through Friday)
Issued at 210 PM CDT Fri Sep 11 2020
As the upper level shortwave moves east through the area on
Saturday evening, scattered showers will be seen across the area.
There will be very little additional rain from these showers.
Tuesday continues to look like it will be rather windy. 950 to
900 mb lapse rates will climb to around 9C/km ahead of an
approaching surface front and shortwave trough. This wind signal
has been very consistent signal among the ECMWF ensemble members
for the past 3 to 4 days. They continue to suggest wind gusts of
25 to 40 knots. The GFS model soundings also suggest similar wind
gusts. The NBM looks too low with its wind gusts so raised them by
5 knots which will put most areas in the 25 to 35 knot range.
From Thursday and beyond, the models diverge on the strength of a
trough moving through the area. The ECMWF is much deeper with this
system, so temperatures are much cooler than the GFS and the
operational ECMWF is supported by its ensemble mean. However,
with this said, there is quite a bit of spread among its members,
so confidence is rather low for this time period.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1030 PM CDT Fri Sep 11 2020
Cigs: mostly IFR/LIFR cigs through tomorrow morning as an upper
level trough slowly tracks east across the region this weekend.
Should see improvement Sat afternoon, post cold frontal passage.
Could bump into VFR for a short period Sat evening, but not
anticipating clearing until Sun when the trough axis swings east.
WX/vsby: -dz/shra through the night, shifting east Sat morning.
Expect vsby restrictions into Sat morning. Should get a break, but
cold air a loft coupled with favorable low level lapse rates could
spark sct/isold -shra for the afternoon. Latest meso models not as
enthusiastic as earlier runs - so opting to remove vcsh. Meanwhile,
can`t rule out some isold thunder chances overnight - RAP bufkit
soundings hint at meager instability aloft. Not confident enough to
mention in forecast for the moment, but will adjust if threat
increases.
Winds: east/southeast through the overnight, swinging to the west by
late morning/early afternoon Sat with passage of a cold front. Low
level jet streaks across KLSE overnight, and could result in a short
period of LLWS for KLSE. However, latest RAP trending away from
stronger winds. Will hold onto LLWS for the moment and monitor.
Positioning of jet limits LLWS concerns at KRST.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...JM
LONG TERM...Boyne
AVIATION...Rieck
Area Forecast Discussion
National Weather Service Bismarck ND
1020 PM CDT Fri Sep 11 2020
.UPDATE...
Issued at 1020 PM CDT Fri Sep 11 2020
Shower activity has greatly diminished over the last hour or two,
a trend which has been supported by the 00Z suite of model
guidance. Therefore, we have limited PoPs at 30 percent, which
still may be too high. Otherwise, recent high-resolution models
have trended toward fog developing across portions of central
North Dakota. Both radiational fog and advection fog would seem
possible given breaks in cloud cover and southeast surface flow,
so we have added a patchy fog mention to the forecast through mid
morning.
UPDATE Issued at 713 PM CDT Fri Sep 11 2020
Shower activity has slowly increased in areal coverage across
southern North Dakota, and now extends as far west as the Montana
border. High resolution models are doing an okay job of depicting
this scenario, with the NAMNest, ARW, and NMM performing better
than the HRRR and RAP. PoPs were updated through the night to
reflect these trends. Sky cover was also greatly increased based
on observed trends and pattern recognition. Some patchy fog may
need to be added to south central and southeast North Dakota, but
will wait to see how the situation evolves. This potential fog
would mostly be driven by low level moisture advection.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 141 PM CDT Fri Sep 11 2020
The closed low that is spinning across the Nebraska Panhandle will
slowly drift northeast overnight tonight. As it does it will
advect in some low/mid-level moisture. Some scattered light
showers are possible across south central ND and the James River
Valley this afternoon through overnight. However, dry air
entrainment and weak forcing could limit chances/coverage of
precipitation tonight.
Saturday, the upper-level low moves out and northwesterly flow
aloft moves in. We`ll see much warmer temperatures than today as
an 850 mb warm nose moves in and mixes down with modestly steep
lapse rates. Saturday should be dry as we`ll be in a lull between
two systems. A cold front approaches Saturday night.
.LONG TERM...(Saturday night through Friday)
Issued at 141 PM CDT Fri Sep 11 2020
A weak cold front will slide through late Saturday night and
Sunday morning. Very little moisture and weak upper-level support
means the majority of the area will be dry. Some slight chances of
precip are possible across the far northeast (closer to the
upper-level support).
Upper-level ridging moves in early next week. Above average
temperatures are expected as a result.
By midweek a cold front will bring the next chance for showers
and a cooldown Tuesday or Wednesday depending on which model
solution verifies (GFS Tues. vs ECMWF Wed.)
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 713 PM CDT Fri Sep 11 2020
Ceilings are forecast to lower to MVFR/IFR levels at KBIS and KJMS
this evening, lasting through the night. Scattered showers are
also possible at these sites. Upstream observations indicate that
some lower visibilities due to drizzle or fog may be possible at
KBIS and KJMS overnight, but confidence is not high enough to
mention this in the TAF at this time. Elsewhere, ceilings are
expected to remain at VFR levels, with conditions becoming VFR at
all terminals by Saturday afternoon. Southerly winds this evening
will slowly turn northwesterly on Saturday, generally remaining
under 10 kts.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Hollan
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...Hollan
Area Forecast Discussion...UPDATED
National Weather Service Hanford CA
333 PM PDT Fri Sep 11 2020
.UPDATE...Updated AIR QUALITY ISSUES section.
&&
.SYNOPSIS...Areas of dense smoke from regional fires will
continue to impact the area, lowering afternoon high temperatures
with continued poor air quality. Temperatures will increase into
the middle of next week as a ridge moves into the area. Dry
weather will continue to prevail for at least the next 7 days.
&&
.DISCUSSION...Yet another very smokey day across the central
California interior as the SQF and Creek fires continue to burn
in the Sierra Nevada. The heavy smoke generated by these fires
(along with the others in the Western U.S.) has kept today`s
temperatures to around 80 to 85 degrees in the valley, desert, and
foothill locations. These temperatures are up to 10 degrees below
normal, which is a far cry from the oppressive heat we
experienced last week. The heavy smoke has also help lower any
extreme fire activity today. So there are some benefits to the
smokey conditions in the region, positive thinking! The HRRR
smoke model output continues to show very heavy smoke across the
region tonight through tomorrow evening. This solution does make
sense given the continued light low and upper level winds across
the region. Current thinking is that the dense smoke will not
disperse much if at all tomorrow which will keep our high
temperatures similar to today.
For the extended period, deterministic and ensemble model output
all indicate that a ridge of high pressure will continue to move
into the Four Corners region. This ridge then strengthens through
the middle of next week. Temperatures are expected to increase
back to normal to slightly above normal readings during this
period. The aforementioned ridge will continue to move east into
the central plains by the end of next week, as a deep trough
moves into the Pacific Northwest. Synoptic cooling and increased
onshore flow will lower temperatures to as much as 10 degrees
below average by the end of next week. At this time, no
precipitation is expected across the region for the foreseeable
future.
&&
.AVIATION...
Mainly MVFR visibility in the San Joaquin Valley and IFR
visibility in the Sierra Nevada and adjacent foothills during the
next 24 hours due to smoke from wildfires in the Sierra Nevada.
Elsewhere, VFR conditions will prevail over the central CA
interior for the next 24 hours.
&&
.AIR QUALITY ISSUES...
Please see SFOAQAHNX for an Air Quality Alert
On Saturday September 12 2020...Unhealthy in Fresno...Madera and
Merced Counties and Sequoia National Park and Forest. Unhealthy
for sensitive groups in Kern...Kings and Tulare Counties. Further
information is available at Valleyair.org
&&
CERTAINTY...
The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
an/or to provide feedback.
&&
.CERTAINTY...
The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
an/or to provide feedback.
&&
.HNX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Public/Avn/Fire Wx.....CMC
IDSS/PIO...............Mattarochia
weather.gov/hanford
Area Forecast Discussion
National Weather Service Jackson MS
927 PM CDT Fri Sep 11 2020
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
Ongoing unsettled airmass across the region keeping some
convection going into the evening hours. Have made a few minor
updates for some showers in the north and southeast to continue as
the overall weakening trend continues. Some minor adjustments to
the hourly trends and to expand cloud cover, but overall no major
updates anticipated at this time.
Prior discussion below:
Tonight and Saturday: Continued warmer than normal through the
period with greater rain chances. Mid afternoon satellite imagery
showed flow around an inverted trough extending north from the
northern Gulf over our northeast Louisiana Parishes. This feature
will continue shifting east tonight and bring an increase in
tropical moisture back across our whole CWA from the southeast by
Saturday morning. Satellite derived PWAT was showing around 2.1in
over much of our CWA; up from 1.72in off the morning JAN sounding.
Daytime heating of this moist airmass was leading to the development
of scattered showers and thunderstorms, generally southeast of the
Natchez Trace. This activity will continue spreading west into this
evening before dissipating. Wl not carry pops past midnight and a
very humid night is on tap. Surface dew points were running in the
low to mid 70s this afternoon and wl continue tonight leading to
morning lows in the low to mid 70s. Normal lows run in the mid 60s
at most locations. Saturday the mid level high centered to our east
that has been dominant will continue to weaken as the closed low
spinning over the Plains edges closer to our CWA. The moist tropical
airmass combined with lower heights and daytime heating should lead
to a greater coverage of mainly afternoon showers and thunderstorms
than today. Greatest coverage of storms will be across our
southeast. The clouds and rain will hold more locations to the upper
80s but most sites are expected to top out again in the lower 90s.
Normal highs this time of the year run in the upper 80s. /22/
Saturday night through Next Week...
Deep troughing continues over the western half of the CONUS which
results in a continued sub-tropical ridge over the ArkLaMiss region
through at least Saturday. To kick things off, the deep trough over
the west will slide across the midwest Saturday, combined with
moisture from the Gulf, this will help with increased rain chances
Saturday and Sunday. By Sunday, the previously mentioned trough will
flatten out and stretch across the north, dropping a weak cold front
across which will be another aid in helping diurnal activity across
the ArkLaMiss Sunday and Monday. There may be potential for some
quick heavy down pours ahead of the front Sunday. Dewpoints will
increase into the mid-upper 70s(74-76F) meaning there will be
efficient moisture to support some possible heavy rainfall. Low
temperatures will be in the lower 70s Saturday night and high
temperatures Sunday will be in the upper 80s from the upper 80s
areawide.
As far as the next working week goes, models have came into better
agreement with some synoptic features. Both the GFS and ECMWF
display a ridge building back over the northwest CONUS and troughing
across the midwest/eastern areas Monday. For us here in the Deep
South, our main concern will be thunderstorms due to an organized
area of low pressure just off the coast of the Bahamas. It is
possible within the next 24-48 hours or so that it develops into a
Tropical depression. Regardless, afternoon through early evening
thunderstorms and locally heavy rainfall will be the case for our
region Sunday through at least Thursday. We will continue to monitor
activity in the Gulf and as always keep you updated with the
latest./JNE/
&&
.AVIATION...
00Z TAF discussion:
Decaying convection will keep some vcsh in for the first couple of
hours of the forecast. Generally a VFR TAF with the exception of
HBG/PIB/MEI with the development of IFR stratus near dawn. Given
the areal scope of the precip this afternoon/evening...expect that
that northern edge of the low stratus may stretch back far enough
to the NW to clip JAN/GTR. HRRR at this point comes close... but
only briefly. Will maintain the more optimistic forecast and keep
an eye on overall trends.
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 74 90 74 89 / 19 68 32 71
Meridian 74 90 73 89 / 22 71 27 62
Vicksburg 74 92 74 89 / 22 64 32 65
Hattiesburg 74 90 72 90 / 25 76 25 64
Natchez 73 90 73 89 / 37 68 28 67
Greenville 74 91 73 88 / 21 58 33 60
Greenwood 74 92 73 88 / 18 64 40 69
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
HJS
Area Forecast Discussion
National Weather Service Elko NV
212 PM PDT Fri Sep 11 2020
.SYNOPSIS...Warm and dry conditions will remain through early next
week and high pressure builds across the region. Daytime highs
could reach into the low 90s through the weekend. Haze and smoke
may return to northern and central Nevada late Friday into
Saturday morning.
&&
.SHORT TERM...Today through Sunday evening. Although GOES imagery
highlights clear skies across much of Nevada, smoke from CA/OR
fires is lurking at the horizon waiting for a favorable shift in
the upper air flow before progressing once again over northern NV.
That chance could come during the early morning hours Saturday as
HiRes model guidance and HRRR simulations hint at upper winds
shifting just enough through the 24-36 hrs to pull smoke from
fires over northern CA and western OR into northern NV by tomorrow
morning. Uncertainty is quite high as to the exact timing and
spacial extent of the smoke layers since it depends upon how fast
the upper high re-centers itself over the forecast area through
Saturday evening. But what is certain is that above average
temperatures and dry conditions will move back into northern NV
through the weekend. Some central NV locations could see some
afternoon wind gusts topping 20kts that will only contribute to an
elevated fire weather concern. High temperatures will be largely
in the 80s but some interior locations could see thermometers
topping in the low 90s. Low temperatures will generally be in the
40s to low 50s into next week.
.LONG TERM...Sunday evening through next Friday.
Relatively stable long wave pattern with warm ridge positioned
over the Four Corner states. Pacific trough appears to be in no
hurry on moving onshore, but does place Nevada under southwest
flow aloft. This wind direction may bring smoke and haze from
California wildfires into our region, particularly Humboldt
County. Wind may increase with some gusts to 30 mph across
northern Nevada as a short wave ejects into the Pacific Northwest
on Monday.
The latest operational GFS and EC are in reasonable agreement
that the Pacific trough will be over Nevada by Friday. Not so fast
per the ensemble cluster analysis, where 3 of the 4 clusters keep
the trough along the California coast or over the eastern Pacific
by next Friday. NBM guidance shows a slow cooling trend next week
from near 90 on Monday to the lower to mid 80s on Friday. Nearly
bone dry with respect to any rainfall, maybe a shower over the
northern mountains (north of I-80) next Friday.
&&
.AVIATION...VFR conditions are expected at KWMC KBAM KEKO KELY and
KTPH through Saturday. Smoke layers from wildfires could gradually
advance east and southeast over parts of northern NV Saturday
morning. There is a risk for MVFR conditions at KWMC and KBAM as
the smoke thickens later in the forecast period.
&&
.FIRE WEATHER...No real changes in the general warming and
continued dry conditions across the region through early next
week. Although relative humidity values will sink back into the
single digits with afternoon wind gusts approaching 20 kts across
parts of northern and east central Nevada, the region will for the
most part remain below critical criteria into early next week.
&&
.LKN WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
97/88/97/97
Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
647 PM PDT Fri Sep 11 2020
.SYNOPSIS...11/325 AM.
Night through morning low clouds and fog will affect coastal
areas through the middle of next week. Otherwise, mostly clear
skies with smoke layers at times will persist through the period.
Temperatures will generally be near to above normal through the
middle of next week. However, high temperatures will be dependent
upon day to day fluctuations on the density of smoke through the
atmosphere.
&&
.SHORT TERM (TDY-MON)...11/250 PM.
After inspection of local webcams and fog product satellite
pictures, it was decided to extend the dense fog advisory until 11
am this morning. Otherwise, the forecast is in good shape with
today`s highs lowered some because of sunlight attenuation due to
the thick layer of smoke. A quick look at the HRRR integrated
smoke loop shows a steady supply of smoke into the night time
hours tonight. Low temperatures this morning were surprisingly low
in a few zones, so we may need to adjust tonight`s low
temperatures downward a touch. The smoke may be a bit thinner this
morning, as the sun appears as a 200 watt bulb in contrast to the
100 watt bulb we saw in the sky yesterday. We will have to
monitor the smoke closely, in case the HRRR smoke model deviates
from reality. The high temperatures for tomorrow are forecast to
be warmer in most locations, but continued presence of a thick
smoke layer may necessitate a slight downward adjustment. Early
projections from the morning model data are showing a better
presence of marine clouds along the coast, probably a result of
the projected increase in onshore gradients for the upcoming
weekend. It is entirely possible that we will see another round of
dense fog in some coastal sections tonight.
So far, afternoon temperatures for today are working out rather
well, and they seem to be a good guide for the highs tomorrow.
The smoke is expected to hang around through tomorrow, but the
slight thinning today did help temperatures south of Point
Conception warm up about 5 degrees. Satellite pictures are showing
another reinforcing shot of smoke dropping into areas south of
Point Conception at this time. If the sun is capable of producing
shadows again tomorrow, the temperatures for tomorrow will be
about right. If we go back to a 100 watt bulb in the sky tomorrow
with no shadows, later shifts would need to take 5 degrees off the
highs south of Point Conception. The smoke still looks rather
dense north of Point Conception and temperatures have been
lowered accordingly. Depending on the smoke conditions for Sunday,
temperatures should warm up with enough smoke dispersal, or
temperatures may need to be scaled back if the thick smoke
persists.
Aside from challenges created by the smoke, 500 mb heights do not
change much in the short term. There is a faint hint in the cross
sections that the marine layer depth will slowly increase through
the weekend, but patchy dense fog is still a threat through
Saturday morning. The pressure gradients do increase for more
onshore flow each day into Monday.
.LONG TERM (TUE-FRI)...11/250 PM.
By Tuesday, the pressure gradients trend weakly offshore for some
slight warming of high temperatures Tuesday and Wednesday. The
ridge slowly weakens on Wednesday.
By Thursday into Friday, an upper low and associated trough push
into the west coast and northern and central California. This will
decrease heights aloft and increase the onshore flow for cooling
temperatures.
&&
.AVIATION...12/0142Z.
At 00Z, the marine layer depth was around 400 feet deep at KLAX.
The top of the inversion was around 1700 feet with a temperature
near 26 degrees Celsius.
Low to moderate confidence in the current forecast. Higher
confidence in coastal stratus forecast, less confidence in
visibility due to smoke. IFR to MVFR conditions in smoke are
possible at all terminals through Saturday afternoon. LIFR to IFR
conditions are likely for coastal terminals, spreading in through
13Z. VFR conditions should develop at most terminals around 20Z,
likely delayed due to smoke.
KLAX...MVFR conditions are likely through at least Saturday
afternoon due to combination of haze and smoke. There is a 60
percent chance of LIFR to IFR conditions at KLAX due to stratus
between 07Z and 16Z. No wind impacts are expected at this time.
KBUR...There is a 50 percent of MVFR conditions in smoke,
especially during the late night and morning hours. No wind
impacts are expected at this time.
&&
.MARINE...11/120 PM.
Outer Waters... Conditions will remain below Small Craft Advisory
(SCA) levels through Saturday morning. There is a forty percent
chance of SCA level wind in the northern and central outer waters
Saturday evening through Sunday afternoon, then a seventy percent
chance of SCA level gusty wind Sunday evening through mid week
for all of the outer waters.
Inner Waters... Conditions will remain below SCA level across the
inner waters through the forecast period.
There will be locally dense fog with poor visibility over the
coastal waters through midday today and again overnight tonight
through midday Saturday.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
.HAZARD POTENTIAL OUTLOOK (MON-FRI).
No significant hazards expected.
&&
$$
PUBLIC...Sweet
AVIATION...Hall
MARINE...Kj
SYNOPSIS...DB
weather.gov/losangeles
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
903 PM CDT Fri Sep 11 2020
.UPDATE...
Issued at 857 PM CDT Fri Sep 11 2020
Previous forecast remains on track for overnight tonight. The
expectation is for moderate to heavy rainfall rates to become more
prevalent as low-level moisture convergence increases along the
Mississippi River north of St. Louis. Believe the 0Z RAP is on the
right track, which paints the heaviest rainfall totals overnight
in far west-central Illinois. The concern remains for training
showers and embedded thunderstorms to potentially cause flash
flooding. The environment is primed for very efficient rainfall
rates due to near-record precipitable water values and very deep
warm cloud depths (13-14 kft). Dry antecedent conditions and weak
instability are certainly helpful, but the aforementioned
environment may overcome these mitigating factors, at least in
some isolated areas. Ongoing flash flood watch looks on track, so
no changes were made this evening.
Gosselin
&&
.SHORT TERM... (Through Late Saturday Afternoon)
Issued at 325 PM CDT Fri Sep 11 2020
The stationary front which has been hanging over Missouri for the
past few days has finally begun moving northward as a warm front.
the low level wave that is causing the front to drift north is a
reflection of the upper level low which moved from the Four Corners
Region into the Great Plains today. The low will drift slowly east
into the Upper Midwest over the next 24 hours and this slow movement
will dictate the speed of the cold front which is behind the wave as
it moves through Missouri and Illinois. Current indications are
that the cold front will not clear the eastern portions of our area
in south central Illinois until Saturday night.
In the mean time, deterministic guidance shows moderate to strong
low level moisture convergence developing this evening and
continuing into Saturday morning along a pre-frontal trough which
stretches from central into northeast Missouri and west central
Illinois. As with the front, this trough will move very slowly to
the east through Saturday, and the moisture convergence along is
very persistent. P-wats in excess of 2 inches are are indicated on
all deterministic models coinciding with this moisture convergence.
NAEFS and EC ensembles are also showing P-wats in the 97th to 99th
climatological percentiles. Additionally, forecast soundings at UIN
have warm cloud depths in excess of 12,000 feet, very conducive to
warm rain processes. With all this in mind, have issued a flash
flood watch for parts of central and eastern Missouri as well as
west central Illinois for tonight into Saturday morning. 2-4 inches
of rain look likely with locally higher amounts.
The pre-frontal trough moves into east central and southwest
Illinois Saturday morning and southeast Missouri during the
afternoon, but the moisture convergence along it is not as strong,
nor as persistent. That being said, P-wats ahead of the trough are
still over 2 inches, so while flash flooding doesn`t look as likely,
some locally heavy rainfall is possible.
Carney
.LONG TERM... (Saturday Night through Next Friday)
Issued at 325 PM CDT Fri Sep 11 2020
The cold front finally drifts through the forecast area on Saturday
night, with high pressure dropping in behind it. The airmass
associated with this high isn`t particularly cold, but it is drier,
and guidance is showing dew point temperatures in the low to mid
60s on Sunday vs the low to mid 70s ahead of the front on Saturday.
The dry airmass will be with us at least through Tuesday as the high
drifts from the Midwest to the Atlantic coast.
Mass fields in the medium range deterministic models begin to
diverge pretty sharply on Wednesday and look very different from
each other for the latter half of the week. The ECMWF has been the
most consistent with warmer and more humid conditions building into
Missouri and Illinois on Wednesday, while an upper level low moves
over the Hudson Bay. The low carves out a deep long wave trough
over the eastern U.S. and pushes a strong cold front through the mid
Mississippi Valley Thursday night into Friday. The past several
runs of the GFS have not agreed with this at all and have not
developed that long wave trough over the eastern U.S. and have
instead kept the mid Mississippi Valley in weak west-northwest flow
aloft with generally quiet weather for the end of the week. This
morning`s 12Z run of the GFS decided to come more in line with the
EC, but it`s much faster with the upper low and trough, and this
pushes the cold front through the mid Mississippi Valley late
Wednesday! High pressure would then build into the Midwest and move
across the Great Lakes through Friday. I have little faith in the
GFS solution at this time...so have a little closer to the EC and
the ensemble forecasts. This keeps warmer temperatures and more
humid air over the area with a chance for convection each day
Wednesday through Friday.
Carney
&&
.AVIATION... (For the 00z TAFs through 00z Saturday Evening)
Issued at 635 PM CDT Fri Sep 11 2020
The main concerns through Saturday morning will be on low ceilings
and reduced visibilities, mainly due to moderate to potentially
heavy rainfall. The focus tonight will be along/just behind a
slow-moving front, which puts central Missouri northeastward into
west-central Illinois as the region of interest. This includes
KCOU and KUIN, where rainfall should become more widespread late
this evening. In addition, ceilings should lower to IFR, with
visibilities in the heavier rain showers below 3SM. Further east,
the metro terminals likely will be VFR/dry most of the night. Rain
chances increase more toward dawn on Saturday, but rain activity
should be more brief and not expecting the heavier downpours
either. Behind the front, a period of IFR or low MVFR ceilings are
expected for the metro terminals Saturday morning. By afternoon,
any rain threat should shift east of the area with low stratus
slowly lifting and then scattering out. Dry/VFR conditions favored
areawide as a result for Saturday afternoon.
SPECIFICS FOR KSTL:
Dry/VFR conditions are favored through tonight. Will have to keep
an eye on activity not too far west, but current thinking is that
it will remain west of the terminal. Chances of rain along a
slow-moving cold front increase early Saturday morning. Also
cannot rule out a few rumbles of thunder. Behind this front,
ceilings should drop to around 900 feet AGL. Conditions then
should slowly improve late morning into the afternoon hours as the
rain threat shifts east and ceilings lift and then scatter out.
Dry/VFR conditions are expected then for Saturday afternoon and
evening.
Gosselin
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flash Flood Watch through Saturday morning for Audrain MO-Boone
MO-Callaway MO-Knox MO-Lewis MO-Marion MO-Monroe MO-
Montgomery MO-Pike MO-Ralls MO-Shelby MO.
IL...Flash Flood Watch through Saturday morning for Adams IL-Brown IL-
Pike IL.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Pocatello ID
125 PM MDT Fri Sep 11 2020
.SHORT TERM...Tonight through Sunday night. We`re in for a fairly
long stretch of warm and dry weather. Satellite imagery shows a
significant pool of smoke along the Pacific Coast. HRRR smoke model
shows a portion of that migrating through southeast Idaho tonight,
but the main area of smoke should stay offshore until Sunday
night/Monday as upper flow becomes more southwesterly. Temperatures
through the period should be well above normal. Hinsberger
.LONG TERM...Monday through next Friday. The upper ridge axis
shifts east of region early Monday as energy ejects inland from the
trough off the NW coast resulting in a resumption of the SW flow
aloft across the region. The GFS is showing a fairly enhanced SW
flow with potential Fire Weather implications whereas the ECMWF is a
bit more subdued. Either way, we should see a renewed influx of
smoke from the California wildfires at that time. The flow relaxes
some as the ridge expands further north across the region Tuesday as
the low regathers itself off the Oregon/Washington coast. By
Wednesday, the GFS and ECMWF solutions diverge once again. Here, the
GFS favors the low gradually moving inland Wednesday into Friday
with increasing SSW flow aloft across the region Wednesday and
Thursday followed by an influx of moisture and instability showers
and thunderstorms Friday as the low shifts across Oregon. The 00z
ECMWF on the other hand favors a northern branch trough sweeping
south through WRN Canada and east along the Canadian highline
Wednesday and Thursday with a "clipper" like system generating some
showers across the CNTRL mountains and Montana divide as the main
low remains anchored off the NW coast through Friday. Thus model
uncertainty reigns over the latter half of the week and we will
allow the National Blend of Models to work its magic here. Huston
&&
.AVIATION...VFR-SKC conditions with continue through Saturday. Huston
&&
.FIRE WEATHER...Forecast continues to be dry through the period with
high pressure remaining in control. We continue to see Haines index
of 5 and 6 widespread across southeast Idaho through Sunday night. A
slight uptick in winds is expected Monday and Tuesday which,
combined with low RH, takes us close to critical fire conditions on
those days. Hinsberger
&&
.PIH WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Area Forecast Discussion
National Weather Service Portland OR
627 PM PDT Fri Sep 11 2020
.SYNOPSIS...Onshore flow continues through the weekend. Some marine
air seeps inland to gradually removing some of the entrenched smoke.
A trough of low pressure early next week returns chances for showers
to the region.
&&
.UPDATE...Surface observations and web cameras show the smoke is
especially dense across Lane County from the Cascades to the coast
with visibilities at or less than a quarter of a mile. The smoke is
also dense in part of the central Oregon coast range and across the
north Oregon Cascades. Visibilities of a quarter of a mile or less
have the potential to result in traffic delays and collisions
providing a new hazard to this smoke besides the ongoing poor air
quality. Have therefore issued a dense smoke advisory for the areas
mentioned above.
Weather models do not handle smoke well, and do not pick up on the
impacts smoke has on modeled temperatures. We tend to have to cut day
time temperature forecasts 10 degrees or more from what models
forecast when observed smoke is opaque enough to block solar
radiation. Since the models are warmer for the interior valleys than
what we are observing, the pressure in the interior is also too high,
as is the onshore pressure gradient. This means that the observed
onshore winds are weaker than the model forecasts, and that the dense
smoke will likely remain around through Monday. The onshore winds in
the hrrr model are stronger than what we are observing, and the hrrr
smoke forecast is most likely forecasting relief from the smoke for
the coast and coast range too early. The current dense smoke advisory
is out through Saturday night, but will likely need to be extended in
time or changed in areas throughout the weekend. ~TJ
PREVIOUS SHORT TERM...From 248 PM PDT...Tonight through Monday...Dry
stable conditions will continue through the weekend as upper level
ridging just off the coast slowly shifts east and breaks down.
Surface high pressure along the coast is bringing light onshore flow
along with shallow marine stratus along the coast. Of course thick
widespread smoke across the region is bringing poor air quality. The
smoke is keeping the temperatures down and most models are not
handling it well. The UW-WRF is much closer to reality with highs
inland in the mid 60s to low 70s for the next couple of days. Model
soundings continue to forecast a shallow inversion through the
weekend. Combined with little surface heating do not expect much in
the way of afternoon mixing. Also with the smoke so deep (PIREPs
from east and west of the Cascades this morning has FU TOPS FL120) it
would only mix more smoke down anyway.In coordination with region
air quality agencies an air quality advisory remains in effect
through Monday morning. There is some hope for better mixing on
Sunday and Monday as the onshore flow increases which may help
improve coastal areas. Also with an approaching upper trough the flow
turns to the south to southwest we may see some of the smoke pulled
offshore.
The aforementioned upper trough approaching the region has been
advertised by models over the past several days. While the details
haven`t been pinned down, the overall message is a pattern shift
from upper ridging to southwest flow. This results in more marine
influence inland and enough mixing to help stir some of the trapped
smoke out of the valley.
&&
.LONG TERM...Monday night through Friday...The extended period is
dominated by an cutoff low developing offshore early in the week,
which is reasonably agreed upon in the models. Such cutoff lows are
traditionally not always well handled by models. Current models have
a surface low rotating toward the coast later Mon. This low is
tapping into subtropical moisture coming from the western Pacific.
12Z GFS shows PW values near 1.5" to 1-8" just off the coast Mon
night. Today`s ECMWF & GEFS IVT values greater than 250kg/m/s is
above 80% at our latitude during the same time period. Expect models
to vary on the details over the next couple of days, but it looks
like some much needed and welcome pcpn is likely later Mon/Tue. For
the remainder of next week, the cutoff remains offshore, moving near
of 130W later Thu. This sets up more southerly flow over the region
which tends to bring a showery unstable pattern. This may bring a
slight chance for thunderstorms Wednesday and Thursday over the
Cascades. Temperatures through much of the week are likely to remain
seasonable. /mh
&&
.AVIATION...00Z TAFS: Current observations across the region are
showing visibilities continuing to be at or below 2SM with the
smoke registering as a deck around 015 to 025 ft. Winds are
light and variable across the region and this trend is expected
to continue into tomorrow. Stratus and southerly winds will
continue to produce a deck around 003 ft into tomorrow. Expect
persistence to be the forecast for the next 24 hours.
Refer to http://weather.gov/zse for detailed regional aviation
weather and hazard information.
KPDX and APPROACHES...Smoke will continue to produce IFR to LIFR
conditions for the next 24 hours. Light and variable winds will
continue to serve as little to no help dissipating the smoke.
-BPhillips
&&
.MARINE...Low pressure near 44N, 136W will continue to bring
southerly winds across the waters into tomorrow morning. Winds
will pick up Saturday afternoon in the outer waters as a weak
cold front approaches the coast. Winds will stay below SCA
criteria during this time. Seas will remain less than 5 ft as
weak swell trains and weak wind waves occupy the waters. There is
potential for stronger winds as a more potent front moves in
Monday into Tuesday. Winds could reach SCA criteria but waves
will likely stay at or below 5 ft. Smoke across the waters,
particularly the nearshore will reduce visibility less than 1
mile in most areas. -BPhillips
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Dense Smoke Advisory until 11 PM PDT Saturday for Cascade
Foothills in Lane County-Cascades in Lane County-Central
Coast Range of Western Oregon-Central Oregon Coast-
Northern Oregon Cascade Foothills-Northern Oregon Cascades-
South Willamette Valley.
WA...None.
PZ...None.
&&
$$
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Area Forecast Discussion
National Weather Service Reno NV
226 PM PDT Fri Sep 11 2020
.SYNOPSIS...
Dense wildfire smoke will bring degraded air quality through the
weekend. Light afternoon breezes are expected today and Saturday.
Winds will then increase Sunday through much of next week. Some
cooling along with a few light showers near the Oregon border are
possible by the middle to the end of next week.
&&
.DISCUSSION...
The primary weather concern for this weekend is the ongoing air
quality and visibility degradation due to smoke. Then, starting
late Sunday afternoon, breezy afternoon winds will create fire
weather concerns each day Sunday through Wednesday.
For discussion of the upcoming elevated fire risk, please see the
fire weather section below.
Regarding the smoke impacts through Sunday: HRRR smoke computer
model indicates light westerly flow will continue to push smoke from
the multiple ongoing California wildfires into northeast CA, the
Sierra and into western NV. The worst conditions are likely from
evening through morning as smoke settles into valleys overnight,
with slow improvements each afternoon. A Dense Smoke Advisory
is in effect through Sunday morning.
Regarding the outlook for the 2nd half of next week: Afternoon
breezes may be fairly light Wednesday with ridging and weak
southwest flow aloft. Then, the offshore trough moves closer to
the coast, possibly bringing an uptick in winds Thursday along
with a tightening of Sierra-to-Great Basin thermal gradients and
also slight chances of light rain north of Susanville. Forecast
confidence in this scenario is increasing -- however, the timing
(which day?) and track (how far south?) of this offshore low is
still fairly uncertain. JCM
&&
.AVIATION...
Smoke will remain an issue this weekend, with the potential for
surface visibility to drop into IFR, especially overnight into the
morning hours. Slantwise visibility will be quite poor with
terrain obscuration also expected due to smoke. Some improvement
is possible each afternoon outside of areas immediately downwind
of ongoing wildfires, however, skies will certainly not be clear.
Winds will generally be light today and Saturday, under 10 kts, with
winds picking up late Sunday and then again each afternoon for
much of next week. We could see wind gusts reaching 25+ kts each
afternoon. JCM
&&
.FIRE WEATHER...
Changes made this forecast cycle:
*Increased afternoon/evening winds for most of next week.
*Increased overnight humidity for mid through late next week.
Warm temperatures, dry conditions, and widespread smoke continues
for this weekend with poor humidity recoveries overnight. Upper
slopes and ridges may only see overnight RH in the teens to mid
20s through Monday morning. Winds are forecast to be on the
lighter side for this afternoon and Saturday, mainly from the
west...hence the smoke. Having said that, zephyr winds are
possible during this time, especially if daytime temperatures warm
a bit out in the Basin and Range. Some smoke improvement is
expected for our eastern zones in the afternoon hours, so it is
possible that a zephyr wind does develop today and Saturday
thanks to the temperature gradient.
By Sunday, southwest winds increase in the afternoon as the
pressure gradient tightens towards the northwest. An enhanced
zephyr is likely at this time with gusts reaching up to 25-30 mph
for wind prone locations. This, along with humidity at or below
15% across much of the region, could generate some localized areas
of critical fire conditions. Best chances would be for the Sierra
Front region, eastern portions of Lassen/Plumas counties, and
extending into northern Washoe County.
Our attention then turns to Monday and Tuesday afternoons as the
gradient looks to continue to tighten in response to low pressure
off the Pacific Northwest coast and high pressure over the Four
Corners. Gusty west-southwest winds are looking more likely during
this time accompanied by low humidity. This would lead to more
widespread critical fire conditions for the areas previously
mentioned, possibly including the southern Sierra Front region. As
of now, we have more confidence in Monday than Tuesday, but we
will continue to monitor to see if updates are needed.
Most of next week does look to remain breezy/gusty during the
afternoon and evening hours with relatively low humidity.
Models do indicate overnight RH beginning to improve by Wednesday
night through the end of next week, but do not let that get your
guard down because even with the higher RH, gusty winds will
spread fire. -LaGuardia
&&
.REV Watches/Warnings/Advisories...
NV...Dense Smoke Advisory until 11 AM PDT Sunday NVZ001>005.
CA...Dense Smoke Advisory until 11 AM PDT Sunday CAZ070>073.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Seattle WA
812 PM PDT Fri Sep 11 2020
.SYNOPSIS...Smoke from wildfires will remain an issue into the
weekend resulting in air quality issues across the whole region. A
frontal system for the start of next week looks to bring showers to
the area for some much needed rain.
&&
.SHORT TERM /TONIGHT THROUGH MONDAY/...Substantial smoke remains
near the surface across the lowlands this evening with cameras
suggesting the heaviest concentrations below 4000 to 5000 feet. HRRR
smoke model output suggests that thicker smoke aloft will arrive
overnight. Unhealthy to locally hazardous air quality conditions
will persist into Saturday. Low level onshore flow continues and
stratus along the coast will make a steady march inland overnight to
reach Puget Sound well before sunrise. It will burn off by midday,
but high temperatures on Saturday will drop a few more degrees as
marine air and thick smoke holds temperatures in the 60s to lower
70s.
Upper ridging continues to weaken on Sunday with low level onshore
increasing a notch. Models are still on track to bring some much
needed precipitation chances by late Monday into Tuesday as a closed
upper low now well offshore of California finally merges with an
upper trough moving down the B.C. coast. No forecast updates
anticipated this evening. 27
Previous discussion...The main story is the wildfire smoke and air
quality issues across the whole region. Given the flow pattern and
abundance of smoke, we`ll likely continue to see air quality issues
through the weekend, with conditions possibly improving as we move
into Monday. Most areas this afternoon are seeing AQI values in the
Very Unhealthy to Hazardous range. And the visibility in the smoke
has been 3 miles or less with just filtered sunshine. As a result,
temps have been trending a good 10 degrees cooler than forecast
guidance with most areas in the 60s. We`ll see these conditions
continue on Saturday and Sunday.
A frontal system will move inland on Monday (mainly Monday afternoon
or Monday night) bringing much needed rain to the region. This,
along with a stronger air flow pattern and deeper mixing will help
clean things out (at least for areas west of the Cascades). So
improvements are on the way. 33
.LONG TERM /TUESDAY THROUGH FRIDAY/...Rain lingers as we move into
Tuesday under moist, SW flow. An upper low will continue to send
showers into western WA Wed-Fri as it slowly moves inland. Chances
are low but we may see a few thunderstorms along the Cascade
crest during this period. However, wetting rains are expected and
the fire weather danger will remain low. Temperature trends remain
close to normal with high temps in the 70s. 33
&&
.FIRE WEATHER...With the return of onshore flow humidities will
continue to climb each day and nighttime recovery will be much
better than they`ve been over the past few days. For air operations,
smoke over the region will present a problem for visibility as well
as low marine layer clouds and areas of morning fog. The marine
layer will be deeper each day and push into the west slopes of the
Cascades over the weekend. The stratus did not make it all the way
around the Olympics this morning, but it should over the weekend.
Although fuels will remain dry, critical fire weather is not
expected as the humidity climbs and precipitation becomes
increasingly likely across Western Washington next week as a weather
system slowly moves into the Pacific Northwest. Whether
precipitation next week is heavy enough to be considered a
wetting rain is a little hard to say, but at least temps will be
much closer to average and varying degrees of onshore flow will
push marine layer moisture into Western Washington.
&&
.AVIATION...Northwesterly flow aloft will transition more west-
southwesterly early Saturday morning. Vsbys will remain diminished
through Saturday due to smoke. Vsbys of 1 to 3 SM will be common at
all TAF locations. Areas of dense smoke are not out of the question.
Not much in the way of vsby improvement Saturday afternoon as winds
remains rather light.
A stronger marine push tonight will push MVFR to IFR stratus into
the Puget Sound and inland areas between 06z and 12z. Cigs will
slowly scatter out and lift on Saturday by early afternoon. Winds
will be light tonight into Saturday with southwesterly winds under 5
knots. JD
KSEA...Smoke through Saturday with vsbys ranging from 1 to 3 SM.
There is the possibility for areas of dense smoke to develop tonight
into Saturday morning as smoke settles and thickens. Cigs will
diminish tonight as marine stratus pushes in. MVFR cigs will lower
late tonight with IFR possible briefly Saturday morning. Ceilings
will be MVFR through much of the morning before some improvement
into the early afternoon. Winds will be light southwesterly at 3 to
6 knots. JD
&&
.MARINE...Smoke for poor visibilities over the coastal and inland
waters through Saturday. Areas of dense smoke are possible through
the afternoon.
Onshore flow through the weekend. Small Craft Advisory winds for the
central and eastern portions of the Strait of Juan de Fuca this
evening. A front will move through the waters Monday night and
Tuesday bringing a chance for showers across the area.
Offshore, swells will generally remain westerly through midweek at 3
to 4 feet.
Pullin/JD
&&
.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 8 PM this evening to 2 AM PDT Saturday
for Central U.S. Waters Strait Of Juan De Fuca-East
Entrance U.S. Waters Strait Of Juan De Fuca.
&&
$$
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